The Conservative party has become increasingly tribal over Brexit. Its 314 MPs have organised themselves into voting groups in an effort to see through their different visions for leaving the EU - or in the case of one bunch, to try to stop Brexit.

These tribes are not strict voting caucuses. Some MPs ignore their group’s instructions, while others belong to more than one caucus.

But the MPs tend to vote in accordance with the groups they are members of, which makes prime minister Theresa May’s task of seeking to get parliamentary approval for a Brexit deal all the more complex.

It was already difficult for Mrs May because the Conservatives lack a majority in the House of Commons, and MPs emphatically rejected her withdrawal agreement with the EU last month. She is now trying to overhaul the agreement with Brussels — before then asking the Commons to vote on a revised Brexit deal.

The Financial Times has gained access to the private membership lists of the groups to which backbench Conservative MPs are affiliated.

Given the secretive nature of the caucuses, there may be some anomalies in the lists. But, taken together with the MPs who are members of the government, these details help make sense of the multiple votes on Mrs May’s Brexit strategy.